Do chimpanzees build comfortable nests?

Nests built by wild chimpanzees (Pan troglodytes verus) were studied at the Fongoli research site in southeastern Senegal from January 2004-May 2004 to investigate the role of comfort in nest building behavior by relating measures of nest comfort and building effort. Nest comfort across zones of the nest surface were compared with construction effort for 25 nests. Several variables of nest comfort were assessed: (1) physical discomfort, (2) visible discomfort, and (3) softness. Physical discomfort was used as a representative measure of nest discomfort. Building effort was measured by (1) construction force, (2) complexity, and (3) added material. Spearman rank correlations compared Effort and Comfort measures for both whole nests and central versus edge zones. The results show that construction force and complexity do not influence comfort of the nest as a whole. Greater Construction force correlates with more nest edge discomfort, yet the central area shows no difference. More complex nests do result in a more comfortable central area in the nest. Nests built with greater force may result in more discomfort, whereas complexity may allow chimpanzees to maintain comfort in a central area for sleep. Chimpanzees may place additional leaves or twigs over hard branches, protruding from the nest surface after construction, to increase comfort of the central nest area. Functions of chimpanzee nest building are likely to be several, but these results suggest comfort is a factor in nest building behavior.     

Do chimpanzees know what conspecifics know?

We conducted three experiments on social problem solving by chimpanzees, Pan troglodytes. In each experiment a subordinate and a dominant individual competed for food, which was placed in various ways on the subordinate's side of two opaque barriers. In some conditions dominants had not seen the food hidden, or food they had seen hidden was moved elsewhere when they were not watching (whereas in control conditions they saw the food being hidden or moved). At the same time, subordinates always saw the entire baiting procedure and could monitor the visual access of their dominant competitor as well. If subordinates were sensitive to what dominants did or did not see during baiting, they should have preferentially approached and retrieved the food that dominants had not seen hidden or moved. This is what they did in experiment 1 when dominants were either uninformed or misinformed about the food's location. In experiment 2 subordinates recognized, and adjusted their behaviour accordingly, when the dominant individual who witnessed the hiding was replaced with another dominant individual who had not witnessed it, thus demonstrating their ability to keep track of precisely who has witnessed what. In experiment 3 subordinates did not choose consistently between two pieces of hidden food, one of which dominants had seen hidden and one of which they had not seen hidden. However, their failure in this experiment was likely to be due to the changed nature of the competition under these circumstances and not to a failure of social-cognitive skills. These findings suggest that at least in some situations (i.e. competition with conspecifics) chimpanzees know what conspecifics have and have not seen (do and do not know), and that they use this information to devise effective social-cognitive strategies. Copyright 2001 The Association for the Study of Animal Behaviour.     

Do vertically transmitted symbionts co-existing in a single host compete or cooperate? A modelling approach

When several symbionts infect simultaneously the same host (multiple infections), the interactions between them affect the dynamics of the symbiotic population. Despite their widespread occurrence, associations with multiple vertically transmitted symbionts have attracted little attention. Vertical transmission tends to homogenize the symbiotic population because of the bottleneck that occurs at transmission. However, fitness advantages conferred on the host by the different symbionts or the induction of reproductive manipulations can make it possible for multiple infections to persist. We used a matrix population model to understand the kind of interactions that can emerge between vertically transmitted symbionts in established multiple infections. Selection acts only to maximize the production of multiply-infected offspring. For a wide range of parameters, this condition allows cooperation between symbionts to be selected for, through their co-transmission, even when it generates additional costs for female fecundity, a reduction in individual transmission, or affects the dependence upon other symbionts.     

Symbolic communication in wild chimpanzees?

The language abilities of captive chimpanzees give rise to the question of the existence and use of similar capabilities in wild chimpanzees. In Taï forest, wild chimpanzees seem to use drumming on buttressed trees to convey information an changes of travel direction, resting periods or both information combined. This communication system is iconic and relies on some arbitrariness. Emergence of symbol-like communication in wild chimpanzees seems mainly dependent on a low visibility environment, a high predation pressure and a large group of males.     

'Friendship' for fitness in chimpanzees?

It has been repeatedly suggested that primates trade social services for fitness benefits in their relationships with the opposite sex. We tested this proposal in a colony of captive chimpanzees, Pan troglodytes, by examining behavioural data on grooming, agonistic support and food sharing in relation to genetically established paternity. We found no support for the notion of trade. First, males did not sire more offspring with females that they actively groomed more frequently, that they supported more often or with which they shared food more frequently. Correspondingly, females did not give birth to more offspring sired by males from which they received more services. Second, males that showed more affiliative behaviour towards females in general did not sire more progeny. Furthermore, females did not bear more offspring sired by males to which they themselves directed more sociopositive behaviour. Results from this captive colony are compatible with those reported for chimpanzees under natural conditions. Copyright 1999 The Association for the Study of Animal Behaviour.     

Why do chimpanzees have diverse behavioral repertoires yet lack more complex cultures? Invention and social information use in a cumulative task

Humans are distinctive in their dependence upon products of culture for survival, products that have evolved cumulatively over generations such that many cannot now be created by a single individual. Why the cultural capacity of humans appears unrivalled in the animal kingdom is a topic of ongoing debate. Here we explore whether innovation and/or social learning propensities may constrain the ability of one of our closest living relatives, chimpanzees (Pan troglodytes), to master an extractive foraging and tool-use task designed to afford opportunities for cumulative culture to develop. We further explore the potential demographic characteristics associated with novel task solutions. Chimpanzees (N = 53) were inventive, flexibly exploring the novel task, albeit complex inventions were rare and shaped by prior individual experience with similar tool-use tasks. However, they displayed no evidence of cumulative cultural learning. Communities displayed richer behavioral repertoires and had greater task success than chimpanzees tested in an asocial control condition, but their solution complexity did not surpass what individuals invented. The lack of social transmission of complex and beneficial solutions in contexts like those we studied provides one explanation for the limited cumulative culture observed in this species.     

Do bonobos copulate more frequently and promiscuously than chimpanzees?

The copulatory activities of bonobos (Pan paniscus) of Wamba, Zaire, were compared with those of chimpanzees (P. troglodytes schweinfurthii) of Mahale, Tanzania. The copulation rates of adult male bonobos were equal to or lower than those of adult male chimpanzees. The copulation rates of adult female bonobos were approximately equal to those of adult female chimpanzees who were in maximal genital swelling, but it should be much higher than those of the adult female chimpanzees throughout the birth interval. The copulation rates of adolescent male bonobos were lower than those of adolescent male chimpanzees, whereas the copulation rates of adolescent female bonobos were much higher than those of adolescent female chimpanzees. It was suggested that the bonobos of Wamba did not copulate more promiscuously than did the chimpanzees of Mahale. The female bonobos may show “receptivity”, whereas female chimpanzees may show rather “proceptivity”.     

Do "savanna" chimpanzees consume C4 resources?

Several stable carbon isotopic studies have shown that South African australopiths consumed significant quantities of C(4) resources (tropical grasses, sedges, or animals that eat those foods), but relatively little is known about the consumption of such resources by chimpanzees. Here, we present stable carbon isotopic data for 36 chimpanzee hair samples from Fongoli, one of the driest and most open areas inhabited by chimpanzees. These data suggest that the Fongoli chimpanzees consume little in the way of C(4) vegetation or animals that eat such vegetation, even though these resources are locally abundant and preferred fruits are more widely scattered than at most chimpanzee study sites. The homogeneity of the Fongoli results is especially striking and recalls the narrow isotopic distribution of stenotopic savanna mammals. This is in stark contrast to what has been observed for australopiths, which had highly variable diets and consumed about 35% C(4) vegetation on average. Carbon isotope data for modern and fossil Papio depict a dietarily variable genus with a tendency to consume C(4) vegetation. This trophic flexibility, or willingness to consume C(4) savanna resources, may make Papio a more profitable ecological analog for australopiths than chimpanzees.     

Do helminths play a role in carcinogenesis?

Chronic helminthiasis is recognized as a significant factor in cancer development in humans. However, the mechanisms by which helminths initiate and promote malignant transformation of host cells are still not understood fully. Human helminthiasis can cause genetic instability and affect inter- and intracellular communication, ultimately leading to tumour development through inflammation, modulation of the host immune system, and secretion of soluble factors that interact with host cells.     

Do facts have a place in science?

The use of the word ‘fact’ in science is discussed. It is suggested that the everyday meaning of the term is assumed when it is used in science and that this can create problems. Some possible ways of overcoming these difficulties are indicated.     

How do learning issues relate with content in a problem-based learning pathophysiology course?

The relation between learning process and content coverage is becoming increasingly important for the understanding of the effects of problem-based learning (PBL) on students' learning. In our medical school, PBL is used as a major educational strategy in the discipline of pathophysiology. A computer program was developed allowing students to register learning issues identified as needed during tutorial sessions and learning issues stated as covered during the individual study periods. In our study, we compared "planned" (learning issues identified during PBL sessions) and "accomplished" learning issues (covered after the independent study periods) identified by pathophysiology students from three consecutive years. We found that the planned learning issues raised during tutorial sessions related to the issues effectively accomplished during the independent study and that their number grew stepwise from basic to preclinical to clinical sciences. Pathophysiology was, globally, the most mentioned discipline. Moreover, the most mentioned disciplines from the basic, preclinical, and clinical areas were physiology, histopathology, and internal medicine, respectively. The single-discipline approach did not limit the student's capacity to identify and cover learning issues beyond the objectives of pathophysiology.     

Why do male chimpanzees defend a group range?

Male chimpanzees, Pan troglodytes, cooperate to defend a community range within which resident females range in smaller core areas. There has been debate over exactly what males are defending, whether mates, territory or both. One hypothesis holds that males are defending mates, and that an increase in community range size will lead directly to the acquisition of more females. However, males frequently attack females as well as males at the edge of the community range. We examined 18 years of observational data on the Gombe chimpanzees to determine the behaviour of males during extragroup encounters, and the consequences of changes in community range size on the number of adult females and indirect measures of food availability. Males were always aggressive to males from other communities, and often attacked adult females, especially those that were not sexually receptive, were older, and/or had more than one offspring. The number of females did not increase with range size, but several measures suggested an increase in food availability with range size. These measures include more time spent in large foraging parties, higher encounter rates with resident females, more encounters with sexually receptive females and higher female reproductive rates. These findings suggest that males defend a feeding territory for their resident females and protect them from sexual harassment. Although a large range may eventually attract more females, this is not an immediate consequence of range expansion. Male number was not correlated with community range size.     

Do you have a probiotic in your future?

The possibility of using microbes to maintain health, and to prevent or treat disease is a topic as old as microbiology. However, one factor impeding the introduction of effective probiotics has been our very limited understanding of the composition of the human microbiome, as well as the biological requirements for these organisms. With advances in understanding the microbiome and its metagenome in humans and other mammals, we now can build a more robust scientific basis to develop probiotic strategies. Increasing knowledge of intramicrobial competition and cooperation, as well as host-microbe cross-signaling, will facilitate design of new probiotics and the modeling of their deployment, leading to eventual clinical trials.     

Perceptual learning: is V1 up to the task?

Our ability to make fine visual discriminations improves with practice, and so at some level so must our visual system. A new paper reports that the receptive field structure of a neuron can be fine-tuned for different visual tasks. These findings raise important questions about the circuitry and mechanisms that underly perceptual learning.     

Enhancement of performances in a learning task in suckler calves after weaning and relocation: Motivational versus cognitive control?: A pilot study

Weaning in suckler calves influences performance in a learning task. The aim of the present study was to investigate whether the improved performance after weaning, including relocation, is due to differences in motivation for the reward or in learning abilities. Forty Aubrac calves were used; half of them were weaned from their dams at around eight months, the other half were weaned one month later. After weaning, calves were housed in groups of four in a new setting. From the day after weaning of the last group of calves, the animals were subjected to two tests: (1) an arena test, (2) a T-maze test where one arm led to either a social or a food reward. The T-maze test consisted of three sessions: in Session 1, trials were conducted until the animal acquired the task (i.e. did not take the unrewarded arm on three consecutive trials); in Session 2, the motivation for the reward was assessed via the walking time of the animal to reach the reward; in Session 3, the place of reward was reversed and the animals were trained until they acquired the new task.

Calves weaned for one day explored more (P < 0.05) and had lower heart rates during the arena test (P < 0.05) compared to the ones weaned for one month. During the T-maze test, calves weaned for one month versus one day did not differ in their capacities to learn the initial route (Session 1) or in their motivation for either the social or food reward (Session 2). Calves weaned for one day learned significantly faster (P < 0.05) the reversed route (Session 3) than calves weaned for one month. Hence, the better performances at reversal in the T-maze by calves that have just been weaned cannot be accounted for by a higher motivation for the reward. A better cognitive control of their behaviour due to a lower stress state is suggested by our results.     

Did brain-specific genes evolve faster in humans than in chimpanzees?

One of the most distinctive characteristics of humans among primates is the size, organization and function of the brain. A recent study has proposed that there was widespread accelerated sequence evolution of genes functioning in the nervous system during human origins. Here we test this hypothesis by a genome-wide analysis of genes that are expressed predominantly or specifically in brain tissues and genes that have important roles in the brain, identified on the basis of five different definitions of brain specificity. Although there is little overlap among the five sets of brain-specific genes, none of them supports human acceleration. On the contrary, some datasets show significantly fewer nonsynonymous substitutions in humans than in chimpanzees for brain-specific genes relative to other genes in the genome. Our results suggest that the unique features of the human brain did not arise by a large number of adaptive amino acid changes in many proteins.     

Use of leaves to inspect ectoparasites in wild chimpanzees: a third cultural variant?

We report 26 cases of using leaves as tools with which wild chimpanzees (Pan troglodytes schweinfurthii) in the Sonso community, Budongo Forest, Uganda, appeared to inspect objects removed during grooming. Careful removal of potential ectoparasites and delicate lip or manual placement on leaves followed by intense visual examination characterised this behaviour. It appears to be done to judge whether either ingestion or discarding is most appropriate, the former occurring in most cases. This behaviour may represent a third variant of ectoparasite handling, different from those described at Taï and Gombe, yet sharing features with the latter. These two East African techniques may thus have evolved from leaf grooming.     

Does dynamical synchronization among neurons facilitate learning and enhance task performance?

Synchronization among groups of neurons is an interesting yet mysterious mechanism in the brain. We propose and demonstrate that the adjustable timing of neural activities can produce profound effect on learning and task implementation. On one hand, learning of more complex patterns becomes possible because of the enhanced capability of classification. On the other hand, implementation of a complex task is aided through active maintenance and control of multiple rules and items. This sheds light on the development of new intelligent system, as well as the cause of impaired learning and task performance in patients.     

Empathy in chimpanzees: Evidence for theory of mind?

Empathy can be widely defined as the capacity to understand the emotional, visual, or cognitive perspective of another individual and is perhaps reliant on the ability to attribute mental states. Behavioural events that may indicate empathy in chimpanzees,Pan troglodytes, are collated (1) using a questionnaire and (2) from the literature. These case studies are classified in a taxonomy of empathic acts in which empathy is categorized as visual empathy, emotional empathy, concordance and extended empathy. In addition, the circumstances surrounding the empathic acts are discussed: whether the recipient of the empathic act was a relative, an unfamiliar individual, or a heterospecific. The cost to the animal showing empathy, whether it displayed any levels of intentionality and if it communicated to a third party are also analyzed. Rescuing of an individual from a dangerous social or physical situation is the only category where the animal shows empathy under all the specified conditions. From this preliminary analysis it seems the chimpanzees may be capable of showing empathy across a wide range of circumstances.